Polyphenyl ether compositions useful as functional fluids



United States Patent 3,290,249 POLYlHENYL ETHER COMPOSITIONS USEFUL ASFUNCTIQNAL FLUIDS Glenn R. Wilson, (Iarnhridge, Mass., assignor toMonsanto Research Corporation, St. Louis, Mo, a corporation of DelawareNo Drawing. Filed Dec. 26, 1961, Ser. No. 162,222 3 Claims. (Cl.252-49.7)

The invention relates to liquid fluids of high thermal stability andmore particularly provides functional fluids comprising polyphenylethers and certain organometallic compounds as adjuvants therefor.

The polyphenyl ethers are known compounds which have found wideapplication as functional fluids owing to their very good thermalstability, lubricity, and resistance to foam. For example, they havebeen found to be valuable as hydraulic fluids, heat-exchange media, asatomic reactor coolants, as diffusion pump fluids, as lubricants inmotor operation generally, and particularly as jet engine lubricants.

With recent changes in the design of aircraft engines, there is a demandfor lubricants which will perform satisfactorily under conditions farmore rigorous than ever contemplated in the past. A particularlyimportant requirement for lubricants intended for use in the newlydesigned engines is that their viscosity be unaffected by the hightemperatures to which they are necessarily subjected.

As is known in the art, petroleum lubricants generally comprise, inaddition to the petroleum base stock, aciditives or adjuvants whichimpart specifically desired properties to the base stock, e.g.,rust-inhibitors, antioxidants, extreme pressure-resisting agents,lubricity improvers, detersives, etc. The additives proposed heretoforehave been designed to accommodate the requirements of petroleum basestocks for lubrication in conventional equipment such as internalcombustion engines of the automotive type, diesel engines and the like.One feature in common with respect to these various applications wasthat the temperature of use was not excessive, i.e., it may vary fromabout 40 F. to 400 F. With the advent of extremely high speed aircraftof the jet type, it was found that neither the petroleum base stock northe conventional additives used therewith were practical, because thelubricant and the additives had to be effective at temperatures whichwere above the decomposition points of the known additives, e.g., attemperatures which were generally within the range of 500 F. to 700 F.It was also found that when conventional additives were employed withfunctional fluids having higher thermal stability than that possessed bypetroleum base stocks, the additives did not perform in a predictablemanner, i.e., a material possessing antioxidant effect or an extremepressure-resisting effect with the petroleum hydrocarbon lubricantsgenerally did not possess such effects when used with the polyphenylether fluids.

Although the polypenyl ethers possess extremely good thermal stabilityat temperatures of, say, over 550 F., they tend to deteriorate, notbecause of a decomposition reaction, but because at the highertemperatures they become quite readily oxidizable. The lubricity of thepolyphenyl ethers is thereby impaired, since the oxidation products donot possess lubricating properties; moreover, the change in viscositywhich is a consequence of the oxidation not only makes for inefliciency,but also may clog up the moving parts of the mechanism which thelubricant was originally intended to protect. Hence, when the polyphenylethers are to be used at the higher temperatures under conditionsrequiring exposure to air, it is necessary to inhibit oxidationphenomena which the higher temperatures favor.

Patented Dec. 6, 1966 Accordingly, an object of the present invention isthe provision of improved polyphenyl ether fluid compositions. Anotherobject of the invention is the provision of polyphenyl ethercompositions having improved antioxidant properties. A most importantobject of the invention is the provision of polyphenyl ethercompositions which possess an improved resistance to oxidation attemperatures of over 550 F.

These and other objects hereinafter disclosed are provided by theinvention wherein there is employed a copper oxide as antioxidant forthe polyphenyl ether liquid fluids. The presently useful copper oxidesinclude cupric oxide (CuO), "cuprous oxide (C11 0), and copper suboxide(Cu O). Cuprous oxide (Cu O) is preferred.

The polyphenyl ethers to which this invention pertains can berepresented by the structure where n is a whole number from 2 to 5. Thepreferred polyphenyl ethers are those having all their ether linkages inthe meta position since the all-meta linked ethers are the best suitedfor many applications because of their wide liquid range and high degreeof thermal stability. However, mixtures of the polyphenyl ethers, i.e.,either isomeric mixtures or mixtures of homologous ethers, can also beused to obtain certain properties, e.g., lower solidification points.Examples of the polyphenyl ethers contemplated are thebis(phenoxyphenyl)ethers, e.g., bis(mphenoxyphenyl)ether, the his(phcnoxyphenoxy benzenes, e.g., m bis(m phenoxyphenoxy)benzene, mbis(p-phenoxyphenoxy)benzene, o bis(o phenoxyphenoxy)benzene, thebis(phenoxyphenoxyphenyl)ethers, e.g., bis[rn- (mphenoxyphenoxy)phenyl]ether, bis[p (p phenoxyphenoxy)phenyl]ether, m-[(mphenoxyphenoxy) (o-phenoxyphenyl)]ether and the his(phenoxyphenoxyphenoxy) benzenes, e.g., m-bis[m (mphenoxyphenoxy)phenoxy] benzene,p-bis[p-(m-phenoxyphenoxy)phenoxy]benzene, or m-bis[m(p-phenoxyphenoxy)phenoxy]benzene. It is also contemplated that mixturesof the polyphenyl ethers can be used. For example, mixtures ofpolyphenyl ethers in which the non-terminal phenylene rings (i.e., thoserings enclosed in the brackets in the above structural representation ofthe polyphenyl ethers contemplated) are linked through oxygen atoms inthe meta and para positions, have been found to be particularly suitableas lubricants because such mixtures possess low solidification pointsand thus provide compositions having wider liquid ranges. Of themixtures having only meta and para linkages, a preferred polyphenylether mixture of this invention is the mixture of S-ring polyphenylethers where the non-terminal phenylene rings are linked through oxygenatoms in the meta and para position and composed, by weight, of about65% m-bis(m-phenoxyphenoxy)benzene, 30% m-[ (m-phenoxyphenoxy)(p-phenoxyphenoxy) benzene and 5% m-bis(p-phenoxyphenoxy)benzene. Such amixture solidifies at about 10 F., whereas the three components solidifyindividually at temperatures above normal room temperatures.

The aforesaid polyphenyl ethers can be obtained by the Ullmann ethersynthesis which broadly relates to ether forming reactions of e.g.,alkali metal phenoxides such as sodium and potassium phenoxides arereacted with aromatic halides such as bromobenzene in the presence of acopper catalyst such as metallic copper, copper hydroxides. or coppersalts.

The copper oxides are combined with the fluid polyphenyl ethers to theextent of 0.01% to 1.0% by weight, depending upon the nature of theoxide and of the ether fluid. The copper oxides have an antioxidanteffect on the polyphenyl ethers, generally. The concentration of copperoxide at which the desired antioxidant effect is obtained is readilydetermined by use of conventional testing procedures known to thoseskilled in the art. The effectiveness of the present additives may notbe the same over the entire range of concentration; for example, whileit has been noted that in most cases the ability of the agent withrespect to anti-wear and extreme pressure lubrication improves markedlyas the concentration is increased, the reverse may be true insofar asantioxidant effect is concerned, lower amounts of the additive oftenresulting in a greater degree of stability to oxidation at the hightemperatures than are attained by use of the greater amounts of the sameadditive.

The invention is further illustrated by, but no limited to, thefollowing examples:

Example 1 In this example, there was employed a mixture of polyphenylethers consisting by weight of 65% of m-bis (m-phenoxyphenoxy)benzene,

30% of m-[(m-phenoxyphenoxy) (p-phenoxyphenoxy)] benzene,

5% 0f m-bis(p-phenoxyphenoxy)benzene.

The rate of oxidation of the above mixture, in the presence or absenceof cuprous oxide or cupric oxide was determined by means of an oxygenabsorption test using a Dornte-type apparatus [J. Inst. Petrol, 41, 283(1955)] equipped with an electrically heated deepwell unit in which thesample was heated by immersion of the test cell. Oxygen was passed, at arate of 12 liters/hour into the test sample maintained at 600 F. andconsisting of either 50 g. of said mixture of ethers or the samequantity of said mixture plus 0.2 percent by weight of one of saidoxides. The mixture of polyphenyl ethers, in the absence of anyadditive, was found to oxidize at the rate of 70 ml. of O /hour. In thepresence of the cupric oxide the rate was reduced to 38 ml. of O /hourand in the presence of the cuprous oxide the oxidation rate was only 18ml. of O /hour. That the decreased rate of oxidation is not due to thepresence of metal was determined by operating in the presence of thesame quantity of minutely suspended copper, zinc or silver. At the endof 4 hours at the 600 F. temperature and the same rate of oxygenintroduction, the following results were noted:

Additive: Ml. of O consumed None 350 Zinc 312 Silver 302. Copper 225Cuprous oxide 72 Example 2 The antioxidant effect of cuprous oxide on apolyphenyl ether fluid was determined by bubbling air through a 20milliliter sample of the mixture of ethers described in Example 1, inthe presence or absence of 0.2% weight of the oxide at 600 F. for 24hrs. at 1 liter/hr., and determining the viscosity (at 100 F.) andpercent loss in weight of the treated sample. The percent change inviscosity (before and after oxidation) was taken as an index ofantioxidant activity. Since some metals had been found to have an effecton the oxidation of polyphenyl ether fluids at high temperatures, thetesting was also conducted in the presence of metals. In order todetermine metal effect, one set of duplicate samples of ether fluidViscosity Increase,

Percent Additive No Wires With Wires None Cuprous oxide The copperoxides possess antioxidant effect for the polyphenyl ether functionalfluids, generally. Thus, instead of the mixture of 65% by weight ofm-bis(m-phenoxyphenoxy)-benzene, 30% by weight of m-[(m-phenoxyphenoxy)(p-phen'oxyphenoxy)]benzene and 5% by weight ofm-bis(p-phenoxyphenoxy)benzene which is used in the above examples, thepolyphenyl ether component may be any one polyphenyl ether having from 4to 7 benzene rings. For example, cuprous or cupric oxide is a very goodantioxidant for any one of the three ethers of the polyphenyl ethermixture of Example 1, as Well as for such other polyphenyl ethers asp-bis- [p-(m-phenoxyphenoxy)phenoxy]benzene, or m-[(mphenoxyphenoxy)(o-phenoxyphenoxy)]benzene, or mbis [m- (p-phenoxyphenoxy) phenoxy]benzene, or mixtures thereof in any proportion. Lubricant mixtures ofethers are generally so constituted as to give simultaneously an optimumof thermal stability and lubricity at the temperatures to which theywill be exposed in operation; but since the polyphenyl ethers,generally, are benefited by the copper oxides with respect to increasingstability to oxygen at high temperatures, mixtures having varyingproportions of the ethers are advantageously modified.

Since the quantity of the copper oxide which is employed with thepolyphenyl ether fluid will vary with the nature of the polyphenyl etherand the nature of the copper oxide, it is evident that no rigid limitsof antioxidant content can be set forth. Generally, polyphenyl ethercompositions comprising from 0.01% to 1.0% by weight of the presentadditive demonstrate antioxidant effect. Determination of the optimumquantities is readily conducted by routine procedures, as will beapparent to those skilled in the art. Hence, the amount of the copperoxide to be used can best be expressed simply as an antioxidant amount.Variations or modification of the compounds and quantities employed inthe examples can be made to accommodate different requirements, so longas the additive belongs to the general class of oxides of copper and thepolyphenyl ether fluid consists of polyphenyl ethers having from 4 to 7benzene rings.

The copper oxides may be used in the polyphenyl ether fluids with otheradditives, e.g., pour point depressants, viscosity index improvers,crystallization suppressants, dyes, etc.

Other modes of applying the principles of this invention may be employedinstead of those specifically set forth above, changes being made asregards the details herein disclosed, provided the elements set forth inany of the following claims, or equivalents thereof may be employed.

What I claim is:

1. A functional fluid composition consisting essentially of a polyphenylether of the formula References Cited by the Examiner UNITED STATESPATENTS 1,632,309 6/1927 Nitardy 252-397 1,992,292 2/1935 Cox et a1252397 3,134,651 5/1964 Kwiatek 260-613 6 FOREIGN PATENTS 851,651 10/1960 Great Britain.

OTHER REFERENCES Aftergut et al., Amorphous Aromatic Compound, Chemistryand Industry, August 29, 1959, page 1091.

Aftergut et a1., Amorphous Aromatic Compounds; the Phenoxypoly(M-Phenoxylene) Benzenes, Chemistry and Industry, Aug. 29, 1959, pp.1090-1091.

LEON D. ROSDOL, Primaiy Examiner.

JULIUS GREENWALD, Examiner.

R. D. EDMONDS, R. D. LOVERING,

Assistant Examiners.

1. A FUNCTIONAL FLUID COMPOSITION CONSISTING ESSENTIALLY OF A POLYPHENYLETHER OF THE FORMULA (PHENYL-O-(PHENYLENE-O)N-)BENZENE WHEREIN N IS AWHOLE NUMBER OF 2 TO 5 AND FROM 0.01% TO 1.0% BY WEIGHT OF A COPPERCOMPOUND SELECTED FROM THE CLASS CONSISTING OF CUPRIC OXIDE AND CUPROUSOXIDE.